Complexation extraction of p-aminophenol（PAP） with bis（2-ethylhexyl）phosphoric acid（P204）,tri-octylamine（TOA） or tri-butyl phosphate（TBP） was studied.The heat of reaction for each extraction was respectively-9.20 kJ/mol,-5.57 kJ/mol,-3.47 kJ/mol.FTIR analysis of the organic phases showed that the extraction mechanism depended on the complexing agent.Lewis acidic complexing agent P204 and Lewis alkaline complexing agent TOA with alkaline functional group —NH2 and acidic functional group —OH of PAP respectively form complexes via ionic association,and neutral complexing agents TBP and TOA with group —OH of PAP via hydrogenbond association.A relationship between the extraction（reaction） enthalpy and the extraction mechanism was found.
